Micro arrays having a matrix of positionally defined reagent target spots for performing chemical tests are known. Known reagents are deposited by spotting techniques well known in the art. In analyzing a sample, it is reacted with the array and separate chemical tests are performed with the reagent at each spot.
Mass spectrometers of various types have been used to identify molecules including proteins by mass analysis. The molecules are ionized and then introduced into the mass spectrometer for mass analysis. In recent years, mass spectrometers have been used by biochemists to identify both small and large molecules including proteins and to determine the molecular structure of the molecules including proteins.
Mixtures of biological compounds are normally separated by chromatographic techniques before the components of the mixture are mass analyzed. In some instances, chromatographically separated components of the mixture are used to create chips or arrays.
In proteomics the aim is to quantify the expression levels for the complete protein complement, the proteome, in a cell at any given time. The proteome is individual, environment and time dependent, and has an enormous dynamic range of concentration. Separation by two dimensional electrophoresis or electrophoresis and creation of spots on an array is cumbersome and slow. Modern analytical methods such as mass spectrometry are used for final analysis of the separated components of the protein complement.
Soft-landing of ions onto surfaces was proposed in 1977 [4] and successfully demonstrated two decades later [5]. Intact polyatomic ions were mass-selected in a mass spectrometer and deposited onto a surface at low kinetic energies (typically 5-10 eV). SIMS analysis was used to confirm the presence of a soft-landed species, C3H10Si2O35Cl+, on a fluorinated SAM surface. Evidence suggests that ions with sterically bulky groups have better deposition efficiencies than small ions [6]. Organic cations [7] and a 16-mer double-stranded DNA [8] (mass ca. 10 kDa) have also been soft-landed intact onto surfaces as have metal clusters [9]. In some of these cases there is evidence that the molecular entity on the surface is the ion, in others that it is the corresponding neutral molecule. There is even evidence [11] that intact viruses can be ionized, passed through a mass spectrometer under vacuum and collected and remain viable.
There is a need for a different separation method coupled with the storage of molecules, including proteins, in an array.